1. Field Of The Invention
This invention relates to sealing lids and sealing lid container combinations, and more particularly, this invention relates to sealing lids which lock in place to seal containers and are especially useful to seal paint containers made of plastic.
2. General Considerations and Prior Art
There are enormous numbers of paint cans and containers manufactured and used both in this country and throughout the world. Almost all paint cans now produced are made of metal with precision-fit lids which have projecting ribs that are frictionally received within a groove in the top of the cans in order to seal the cans. It is becomming increasingly apparent that plastic paint containers have certain advantages over metal cans. A primary advantage is that plastic containers are less expensive. Moreover, plastic containers can be made of materials which are inert with respect to the paint within the containers so that paint is not in danger of contamination by the can. Metal cans are generally made of steel and have a tin coating on the inside surface which is supposed to prevent interaction between the steel and paint. The paint can become discolored rather rapidly if the coating is improperly applied or becomes damaged so that the steel portion of the can is exposed to the paint. With oil base paints, this is not a great problem, however, with water based paints, such as vinyl paints which are becoming increasingly popular, this is an enormous problem because water tends to rust steel. When the rust disperses in the paint, the paint is usually ruined. Accordingly, as the demand for water based vinyl paints increases, so does the demand for quality plastic containers.
In order to be commercially viable, plastic containers must meet certain requirements. One of these requirements is that the containers can be readily substituted for metal cans without necessitating extensive changes in the filling and handling apparatus currently used with metal paint cans. Accordingly, plastic containers should be cylindrical so as to geometrically resemble metal paint cans and should have lids which are axially slid thereon to seal the containers.
One advantage to using the rib-in-groove structure relied on to seal the lids on metal cans is that contamination of paint within the cans due to damage to the tin layer during sealing is avoided. A major disadvantage of this sealing arrangement is that paint tends to collect in the groove so that when the lid is resealed, paint in the groove is displaced on to the lid and down the side of the can. With plastic paint containers this mess can be avoided because there is no need for such a groove. Exemplary of approaches, specifically of interest with respect to plastic paint containers, is applicant's co-pending patent application "Container and Lid of Molded Plastic Material", Ser. No. 917,588, filed June 21, 1978. While this approach has proved quite satisfactory, other approaches are needed because the plastic paint container industry is in its infancy and as it matures it needs a broad, diverse, technological foundation upon which to grow.
Although the foregoing discussion is directed particularly to the plastic paint container industry and that technology specifically developed to solve problems in that industry, the subject invention also has application to problems in other industries. Accordingly, the joint which is effected between the container and lid as described hereinafter may have other uses and applications.